1. Technical Field
The present invention relates to a capacitive input device capable of detecting a position touched by a human finger as a change in capacitance.
2. Related Art
Recent electronic apparatuses such as mobile phones, car navigation systems, personal computers, ticket-vending machines, and banking terminals include tablet input devices disposed on liquid crystal displays. With reference to instruction images displayed on image display regions of the liquid crystal displays, information relating to the instruction images can be input into the electronic apparatuses by the touch of human fingers to the image display regions.
Examples of such input devices include resistive touch panels and capacitive touch panels. The resistive touch panels have a two-layer structure including a glass sheet and a film, which is pressed down to make a short circuit. Therefore, the resistive touch panels have disadvantages that they have a narrow operational temperature range and deteriorate with time.
On the other hand, the capacitive touch panels have an advantage that they have a simple structure including a substrate and a translucent conductive film disposed thereon. For example, JP-A-2007-122326 discloses a capacitive input device including electrode lines extending in directions intersecting with each other. The capacitive input device detects a change in the capacitance between the electrode lines touched by a human finger to identify an input position.
Another type of capacitive input device detects an input position in such a manner that an in-phase, equipotential alternating current is applied between both ends of a translucent conductive film and a weak current generated by the formation of a capacitor due to the approach or touch of a human finger to the translucent conductive film.
There is a problem in that a process for manufacturing the following device is complicated: a capacitive input device that includes a translucent substrate, a plurality of first translucent electrode lines which extend in a first direction and which are disposed on the front surface of the translucent substrate, and a plurality of second translucent electrode lines which extend in a second direction intersecting with the first direction and which are disposed on the rear surface of the translucent substrate.
In input devices, images displayed on liquid crystal displays are viewed through entry screens and therefore, highly translucent substrates and electrode lines are used. When regions containing the translucent electrode lines have a reflectivity significantly different from that of regions containing no translucent electrode lines, the presence of the translucent electrode lines is conspicuous, which is not preferable. On the other hand, the first and second translucent electrode lines are disposed on the front surface and rear surface, respectively, of the translucent substrate, that is, the translucent substrate is located between the first and second translucent electrode lines. Therefore, a region containing the first translucent electrode lines, a region containing the second translucent electrode lines, and a region containing no translucent electrode line are different in optical architecture from each other. This results in large differences in reflectivity between these regions to cause a problem that the first and second translucent electrode lines are conspicuous.